A study on Cylindrospermopsis raciborskii was undertaken in the Anzali Lagoon, a shallow coastal wetland, during the growth seasons in spring and summer of 1992 and 2005. Water samples were collected on a monthly basis from four sampling stations for quantitative and qualitative analyses of phytoplankton species. A Ruthner sampler was used to collect water samples from a depth of 20 cm for the quantitative analyses of phytoplankton while water samples for the identification of plankton species were collected from the entire water column using a plankton net sampler with a mesh size of 25 microns. All samples were fixed in 2% formalin solution. C. raciborski, a freshwater species of the subtropical and pantropical regions was observed in the samples along with 19 other cyanophyta species. Masses of C. raciborskii consisted of filaments that were cylindrical, straight and narrowed towards the end. Cells were cylindrical or barrel shaped 2.5-12(16) × (1.7)2-4 mm. The cross walls were narrow, end cells conical or round. Heterocytes were drop-like with ovoid or pointed terminals. Akinetes were cylindrical or ovoid (7)8.5 - 18(22) mm. Formation of blooms is a distinctive feature of this species and populations of this species produce a kind of cyanotoxin. This species was found abundantly in the western region of the Anzali Lagoon where the pH was above 8. The species C. raciborskii comprising more than 70% of the species composition in the months of July and August was considered the dominant species in this region of the Anzali Lagoon. Owing to the lack of proper environmental management policies, a large amount of sewage (industrial, agricultural and domestic) enters the Anzali Lagoon everyday causing an increase in the organic load and eutrophication of this lagoon thus providing favorable conditions for the occurrence of heavy blooms of C. raciborskii. This will ultimately result in the mass mortality of aquatic organisms.

Cyanobacteria blooms are common in Baltic Sea and their intensity have been increased due to anthropogenic eutrophication. In this study we investigated the cyanotoxin levels in the water samples collected from four different locations in the Baltic Sea at three different seasons including summer 2011. Protein phosphatase 2A (PP2A) inhibition assays, Enzyme-linked immunosorbent assays (ELISA) and liquid chromatography-mass spectrometry (LC-MS) were employed to detect cyanotoxin variants. Microcystin- LR equivalents (MCE) were detected in a number of the water samples collected at site A (0.4 to 0.64 mg MCE/ L) and at site B (0.24 to 0.44 mg MCE/ L). Cyanotoxin concentrations, as measured by ELISA, ranged between 0.98 -7.45 mg MCE/L in samples collected at site A and between 0.12 to 0.68 mg MCE/L, in samples collected at site B. By using LC-MS one of the molecules present in the samples from site A was determined to be nodularin (0.213 to 0.524 mg/L) whereas samples from site B did not contain this toxin nor did they contain any of the most toxic microcystin species mentioned. The data obtained show good correlation with the MC concentration changes measured in samples and these concentrations were relatively higher during warmer months. In addition we also investigated the adsorption of toxins from water into the circulation of grazing cattle and the results show no measureable liver damage resulting from cyanotoxin poisoning.

Cyanobacteria, ancient photosynthetic prokaryotes, form harmful blooms that degrade water quality and pose many risks to human health. The main objective of this study is to identify toxic cyanobacteria present in fish ponds, evaluate their effects on Zebrafish (Danio rerio) tissue, and investigate their characteristics. Samples were collected from the walls and floors of rainbow trout raceway ponds at Alborz Caspian Company, situated in Alborz province, Iran. The purpose of this collection was to isolate and examine cyanobacteria colonies. As a result of meticulous microscopic and macroscopic observations, three pure samples of Calothrix sp., Nostoc sp., and Microcystis sp. species were successfully identified. These samples were then transported to the laboratory and processed using the Z8 solid culture medium within a growth chamber. Cyanobacteria were identified based on their morphology using a light microscope and validated identification keys. The DNA extraction was performed using the cetyl-trimethyl-ammonium bromide method. Zebrafish were acclimated and fed with fish food containing lyophilized cyanobacteria for a period of 30 days. At specific intervals, fish were collected for histopathological analysis and measurement of antioxidant enzyme activity. The histopathological examination of intestinal tissue in the treatment groups exposed to lyophilized cyanobacteria revealed lesions including hyperplasia of enterocytes, reduction in their length, vacuolation of enterocytes, hyperplasia of goblet cells, and infiltration of lymphocytes. The gill samples from the treatment group exhibited severe histopathological abnormalities such as displacement of epithelial cells, fusion of lamellae, epithelial necrosis, and lymphocyte infiltration. These symptoms diminished over time. Hepatocellular lipid changes and vacuolation were observed in the treatment group's liver samples, peaking on the 30th day. The activity of superoxide dismutase (SOD) enzyme significantly increased in the exposed Zebrafish on the 30th day compared to the control group, and similar significant increases were observed on the 20th and 30th days (p<0. 05). There were no significant differences in Catalase (CAT) activity between the control and treatment groups (p>0. 05). Generally, the study identified specific histopathological abnormalities in the fish exposed to lyophilized cyanobacteria and observed changes in antioxidant enzymes activity. These findings contribute to understanding the impact of cyanobacteria on fish health status.

Cyanobacteria are bacteria found in different ecosystems, such as lakes and rocks. These bacteria, capable of photosynthesis, are important sources of oxygen. However, some cyanobacterial strains can produce toxins, which are harmful to humans and animals.Therefore, collection of epidemiological and surveillance data on cyanobacterial toxins in the environment is vital to ensure a low risk of exposure to toxins in other organisms. For presentation of accurate data on environmental cyanobacterial toxins, it is essential to understand their characteristics, including taxonomy, toxin proteins, and genomic structures, and determine their environmental effects on bacterial populations and toxin production. Taxonomy, which is the scientific classification of organisms, is important in identifying species producing toxins. The structure of toxin proteins and their stability in the environment allow researchers to detect toxins with analytical methods and discuss their limitations. Onthe other hand, identifying toxins via molecular typing enables researchers to investigate toxic cyanobacteria by detecting toxin-encoding genes and toxin gene expression. Meanwhile, environmental factors, such as nutrient level, light intensity, and biotic factors, allow researchers to predict the suitable time and location for accurate sampling. In this review, these cyanobacterial features, which are important for accurate detection of cyanobacterial toxins, will be discussed.

Background and Objective: Antibiotic residues from urban and industrial wastewater discharge and agricultural runoff are continuously released into freshwater environments, turning them into reservoirs that contribute to increased antibiotic resistance. Therefore, understanding the effects of antibiotic residues on aquatic organisms, especially cyanobacteria, is essential due to their vital role as primary producers in ecosystems. Materials and Methods: In this review article, over 200 reputable publications related to the effects of antibiotics on major biological processes in cyanobacteria-including photosynthesis, oxidative stress, and macromolecule metabolism-are examined in detail. The mechanisms of their adaptation to antibiotic exposure are also thoroughly reviewed. To this end, searches were conducted in databases such as Science Direct, Scopus, Web of Sciences, and open-access journal lists, using keywords like "cyanobacteria, " "biodegradation and bioremediation, " "bioaccumulation and biomagnification, " "activation of antioxidant systems, " "mechanism of action of a wide range of antibiotics, " synergistic and antagonistic effects, " "acquisition and transfer of antibiotic resistance genes, " and "mutations induced by antibiotics. " Results: The antibiotic resistance developed in microalgae is associated with an increased rate of photosynthesis, antioxidant activity, and toxin production, while oxidative stress and growth decrease. Therefore, the higher presence of cyanotoxin biomass, especially near wastewater treatment plant outlets, may play an important role in the removal of antibiotic resistance genes. Conclusion: There is a direct correlation between the levels of antibiotics and the increased production of microalgal toxins, indicating that microalgae become resistant to antibiotics over time and thus can play a vital role in eliminating the excess ROS generated from antibiotic exposure.